Electric switches or circuit breakers



gsmss Aprifl 8, 195 E. COLEMAN ELECTRIC SWITCHES OR CIRCUIT BREAKERS 2 Sheets-Sheet 1 Filed July 18 1955 Aprifi 11958 E. COLEMAN 8 ELECTRIC SWITCHES OR CIRCUIT BREAKERS Filed July 1a, 1955 2 Sheets-Sheet 2 A Home y ELECTRIC SWITCHES GR CIRCUIT BREAKERS Edward Coleman, Walsail, England, assignor to J. A. Crahtree & Co. Limited, Walsall, England, a British company Application July 18, 1%5, Serial No. 522,789

Claims priority, application Great Britain July 31, 1954 7 Claims. (Cl. 2tltl-=144) This invention relates to improvements in electric switches or circuit breakers and is particularly concerned with arc chambers for the contacts thereof, the principal object of the invention being to provide an improved arrangement of simple and inexpensive construction for ensuring that the chamber is, at all times, isolated from the switch mechanism, thereby excluding the are from the latter and preventing carbonisation from detrimentally affecting the di-electric properties.

According to this invention an insulating shield on the moving contact arm is adapted to close the opening in the are chamber through which the arm extends. The shield may be in the form of a fiat plate guidingly slidable in the arc chamber. The latter may be constituted by a rectangular enclosure made of insulating material and having its front wall aperture-d for the passage of the moving contact arm. This wall may be formed of two spaced strips between which the flat plate slides. The arm extends through an aperture in the plate which is shaped so as to extend beyond the openings in the wall in the on and off positions of the contacts. Thus the plate constitutes an obstructive barrier which completely isolates the arc chamber from the switch mechanism or trip means in all positions of the switch. The improvements enable the arc chamber to be of small dimensions so that on short circuit, the relatively high pressure of gases confined to the chamber, assists in the extinction or stifiing of the are. A known form of magnetic blow-out or de-ion grid may be employed in association with the arc chamber.

In order to enable the invention to be readily understood reference will now be made to the accompanying drawings illustrating by way of example one construction for carrying the invention into effect, in which drawings:

Figure l is a perspective view of a circuit breaker embodying these improvements.

Figure 2 is a perspective view to a larger scale of the circuit breaker with the cover removed.

Figure 3 is a central vertical section of the upper part of the circuit breaker parts being shown in elevation.

Figure 4 is a section on the line IVIV of Figure 3.

Figure 5 is a perspective view of the liner of an arc chamber.

Figure 6 is a perspective view of the shield of an arc chamber.

Referring to the drawings a pair of deep rectangular recesses 1 in a moulded insulating base 2 are separated by a wall 1 Each recess houses a fixed contact 3 and is lined on three sides with insulating material formed for example by bending a fibre sheet 4. The fourth side is closed by a pair of spaced plates 5, 5 trapped in position between the side walls 4* of the bent material, projections 5 on their side edges, entering slots 6 in the side walls 4* for locating the plates in position. The side plates 5, 5 may be secured in staggered spaced relation, by a rivet for holding the plates of a magnetic blow-out or by the plate members 7 of a de-ion grid. These plates 7 are formed with lateral rectangular projections 7*- enteratent' a 2,830,158 Patented Apr. 8, 1958 ing similarly shaped slots 6 in the side walls 4 The plates 5, 5 are formed with extended rectangular openings 5 through which projects a pivotal moving contact arm 8 having one end shaped for engaging a fixed contact 3 and the other end adapted for actuation by the switch or trip mechanism. Each arm 8 is closely engaged by a rectangular aperture in a flat insulating shield 13 and slidable in the space between the fixed plates 5, 5

The length of the openings 5 freely permits the movement of the arms 8 between the on position, as shown in full lines in Figure 3, and the off position as shown in chain lines in this figure. Each pair of plates 5, 5 may be of similar construction, one being disposed slightly forward of the other so that the openings 5 therein conform with the inclined disposition of the contact arm 3 relatively to the base. The shield 13 is slidable, with the contact arm, between the plates 5, 5 its dimensions being such that at all times it obstructs the openings 5 in the plates, thereby serving to isolate the arc chamber from the external mechanism 11 for actuating the contact arm. Each arc chamber may be lined with material such as asbestos for absorbing the heat energy from the arc.

The switch may be manually operated by a dolly 10 acting through a toggle mechanism 11 connected with the moving contacts 8. The toggle may be tripped on the occurrence of an overload by means such as an electromagnet 12 actuating an armature 12 The improvements enable the arc chambers of a multi-pole circuit breaker to be relatively closely disposed in side-by-side relation, thereby enabling the dimensions of the arrangement to be relatively small in order to provide a compact construction.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in the method of operation may be made by those skilled in the art, without departing from the spirit of the invention. it is the intention, therefore, to be limited only as indicated by the scope of the appended claims.

Having thus described my invention, I claim:

1. An air break switch or circuit breaker comprising a base having a recess therein forming a chamber, a fixed contact disposed in said chamber, a pivotal contact arm cooperating with said fixed contact, mechanism for actuating said arm, arc extinction means comprising an atmospherically insulated sealed lining for said chamber whereby said sealed lining retains pressurized gases therein to suppress the arc and isolates such gases from erosive contact with said actuating mechanism during all positions of said pivotal arm.

2. A circuit breaker according to claim 1 wherein one wall of said sealed lining is provided with a multi-bafiled closure comprising a floating shield disposed between two staggered guide plates.

3. A circuit breaker according to claim 1 in which said are extinction means includes a de-ion grid and means for securing said grid to the walls of said lining.

4. A switch or circuit breaker according to claim 2 wherein said shield and said plates are apertured for pivotal movement of said arm therethrough and said armfitting shield is pressed outwardly against one of said plates by pressured gases to seal said chamber.

5. A switch or circuit breaker according to claim 2 wherein said plates are provided with extensions thereon and the walls of said lining are slotted to engage and retain said extensions in spaced relation.

6. A switch or circuit breaker according to claim 1 wherein three walls of said lining comprise a single bent sheet of insulating material.

7. An air break switch or circuit breaker comprising a base having a chamber formed therein, are extinction means, a fixed contact disposed in said chamber, a pivotal contact cooperating with said fixed contact, mechanism' for actuating said pivotal contact remotely' iisposecl from saidfixed contact, a lining having a sealedclosure isolating said chamber from said mechanism during all positions of said pivotal contact, said closure comprising staggered bafile plates .fitting about said pivotal contact and superimposed between a closely fitting floating shield, whereby pressured gases originating in said chamber force saidshield against one of said plates to seal the gases in said chamber from said mechanism.

References Cited in the file of this patent UNITED STATES PATENTS Riddick Apr. 18, 1922 Anderson July 21, 1925 McClure Mar. 14, 1939 Jackson et a1. Dec. 30, 1941 Goldberg July 28, 1942 Baxter June 21, 1949 Bingheinheimer et al May 8, 1951 Gelzheiser et a1 Sept. 27, 1955 

